In the prior art it is known that real-time data processing systems may include a central processor at a central site that is selectably coupled to one of a plurality of line terminals at a plurality of remote sites. These remote line terminals utilize existing telephone line transmission systems to be coupled to the central processor through a communications demultiplexer/multiplexer at the central site. Intercoupling of a particular remote line terminal to the central processor may be initiated by either the central processor or the particular line terminal. In either situation, the central processor must know the terminal characteristics and line speed of the transmitting/receiving line terminal so that the central processor may condition its internal logic circuitry to receive/transmit the digital data in the terminal characteristics and at the line speed that is utilized by the particular line terminal.
In some systems, line speed is known and only the terminal characteristics are to be determined. Such systems may include a hardware system called an answerback circuit for transmitting to the central processor the necessary information that identifies and defines the terminal characteristics -- see U.S. Pat. No. 3,697,961. In those systems in which neither terminal characteristics nor line speed are known, software subroutines or algorithms may be utilized by the central processor to determine unknown terminal characteristics and line speed, -- see the publication "Identifying Terminals in Terminal-Oriented Systems," J. F. Ossanna, IEEE Transactions on Communications, Volume COM 20, No. 3, June, 1972, pp. 565-568. However, software algorithms, when utilized to identify both terminal characteristics and line speeds of a plurality of unknown and remote line terminals of greatly differing terminal characteristics and line speeds, may occupy a significant and disproportionate amount of the central processor's data processing time. Thus, there is a need for a hardware system for automatically determining both the terminal characteristics and the line speed of each of a plurality of remote and unknown line terminals of greatly differing terminal characteristics and line speeds.